ARP:

1. ARP stands for Address Resolution Protocol.
2. It is the protocol used by Internet Protocol (IP) specifically IPv4.
3. This protocol operates below the network layer as a part of the interface between the OSI network and OSI link layer.
4. It is used to map Logical Addresses to the Physical Addresses used by a data link protocol.
5. ARP Simply Converts IP Address to Physical Address.
6. It is relatively simple Request-and-Reply Protocol.

ARP Request & Reply:

1. ARP maintains the mapping between IP address and MAC address in a table in memory called ARP cache.

2. The entries in this table are dynamically added and removed.

3. A host will update its ARP cache, only if the ARP request is for its IP address.

4. Otherwise, it will discard the ARP request.

5. Consider the above figure, in this a Host sends out the Request Message.

6. It is looking for the MAC Address of the node with IP Address 192.168.1.220.

7. The Node with the IP Address 192.168.1.220 sends out the Reply Message.

8. In reply message it sends its MAC Address to the Host.